Voters head to the polls in seven states Tuesday, wrapping up the first half of the 2014 primary season and giving ad-weary voters a month-long breather before competitive races begin again in August. The first half of the season ends with a bang as two congressional warhorses battle to keep their seats of power and rural precincts find themselves blanketed with a windfall of outside money. A look at some of the hottest races and the dollars behind them:

Mississippi Senate

$17 million. That’s the latest tally of political spending in Mississippi’s seemingly unending Republican primary — a mind-boggling figure in a state without one media market among the nation’s top 50. Voters will finally be free of the endless parade of robocalls and attack ads on Tuesday, as voters decide the runoff election between incumbent Sen. Thad Cochran and Chris McDaniel.

Our friends at OpenSecrets.org have been keeping an eye on all the last minute checks fueling the campaigns and outside groups; our Real-Time FEC tracker shows these groups have been spending the cash as quickly as they can raise it. Between the June 3 primary to Tuesday’s final showdown, super PACs and dark money outfits have spent an additional $3.2 million on independent expenditures — TV commercials, Internet ads and mailers aimed at swaying voters in the bitter election.

The U.S. Chamber of Commerce is pulling out all the stops for Cochran, spending $700,000 on the runoff election and even recruiting former Green Bay Packers great Brett Favre, a Mississippi native, for a commercial. But no one has outspent the Club for Growth Action Fund. The hardline conservative group has the distinction of being the highest-spending super PAC in the race, doling out $2.4 million so far in support of McDaniel.

New York-13

Longtime Rep. Charlie Rangel is synonymous with New York politics; a look at his congressional campaignsheds some light into just how deeply entrenched the Harlem Democrat is in the state’s political framework. Harlem powerbroker Basil Paterson was Rangel’s campaign treasurer until his death in April. Basil’s son, former New York governor David A. Paterson, has now assumed the role. The campaign employs an all-star consulting company, Global Strategy Group which counts former governors David Paterson and Eliot Spitzer among its former clients, in addition to maintaining a lobbying presence in Albany.

However, some in Rangel’s district, which straddles upper Manhattan and the Bronx, think its time for a shakeup. Rangel faces a serious primary challenge from Dominican-American state Sen. Adriano Espaillat in a 2012 rematch. Though Rangel has derided his opponent as a political novice with few legislative successes in the state capital, Espaillat’s campaign has managed to contend with the Rangel political machine through strong support from individual donors. Campaign disclosures reveal that more than 90 percent of the itemized donations ($200 or more) to Espaillat came from individuals, rather than PACs, an indication of strong grassroots support in a once-black enclave that’s now more than 50 percent Hispanic.

Political action committees representing labor unions, government contractors and major corporations have all contributed to Rangel’s reelection bid. Even so, Espaillat is not without friends in high places. Eliot Spitzer contributed $5,000; the former governor’s father, billionaire real estate magnate Bernard Spitzer, gave the maximum $5,200 to Espaillat’s campaign.

Rangel lost much of his clout along with his seat as chair of the House Ways and Means Committee after his colleagues censured him for ethics violations in 2010; still, he remains a prolific fundraiser. Campaign disclosures captured by Real-Time FEC show the 22-term Democrat has pulled more than $1.1 million, while his leadership PAC had a little more than $22,000 on hand at the start of the second quarter.

New York-21

New York’s 21st Congressional District is one of the state’s most rural, though you wouldn’t know it by the size of the independent expenditures flowing to the sprawling district. The decision by Democratic Rep. Bill Owens to retire has sparked a competitive Republican primary as conservatives see a chance to flip the centrist district.

Matt Doheny, a wealthy businessman with roots in the area, will be running his fourth campaign for the seat. This go-around he faces intra-party competition from former Bush policy aide Elise Stefanik. Doheny’s had to contend with seven-figure ad campaigns from rival conservative groups affiliated with Karl Rove and wealthy financiers.

American Crossroads, the Rove-linked super PAC, broke from the tactics of past elections by airing negative ads in a Republican primary. The group has invested heavily in the race, spending nearly $800,000 against Doheny in the primary.

The donors behind New York 2014 — a newly-formed super PAC backing Stefanik — were not public until June 20, when the committee’s filing revealed that a clutch of hedge fund managers were behind the new group.

A recent poll from Harper Polling shows Stefanik eight points ahead of Doheny, the Watertown Daily Times reports.

Oklahoma Senate

Dark money. That’s the key factor driving Oklahoma’s Senate battle. Beyond the high-profile endorsements and debates, politically active nonprofits that don’t report their donors to the Federal Election Commission have dominated the airwaves in the Sooner State. State House Speaker T.W. Shannon faces off against Rep. James Lankford in a special Republican primary, where Shannon has benefitted from the lion’s share of the outside spending. The two are vying to become their party’s nominee to replace Sen. Tom Coburn. The veteran Republican lawmaker, who is battling cancer, will retire at the end of the year.

Oklahomans For a Conservative Future seemed to have broken new ground when Sunlight reported that the politically-active group had registered as a for-profit corporation in its home state. Incorporated by state lobbyists and an Oklahoma City construction executive, OCF later changed its status to the more traditional vehicle for dark money groups, a 501(c)4 social welfare nonprofit. It has spent over $900,000, mostly on negative ads aimed at Lankford.

Lankford has also benefitted from dark money, albeit in a much smaller way. The Foundation for Economic Prosperity, another nonprofit, has disclosed spending $100,000 on ads boosting the congressman.

Oklahoma-5

Lankford’s decision to give up his House seat for a Senate run has created a heated contest in Oklahoma’s Fifth Congressional District, which spans Oklahoma city and its environs. The district is solidly red and the winner of the Republican primary is expected to win the general election. In the crowded field of conservative hopefuls jockeying for an edge six-way race, one candidate, state Rep. Michael Turner, has had a little more help than most.

A freshly-minted super PAC, the Democracy Values Fund, jumped into the race in support of Turner. As NewsOK first reported, all of the group’s funders share a last name with the candidate, though the PAC’s treasurer said he did not know if there was any relation. Turner’s family members own several successful businesses in the state, including a trucking company.

A May survey by a local TV station showed Turner vying for the lead with Corporation Commissioner Patrice Douglas and state Sen. Clark Jolley with the candidates separated by razor-thin margins.