NEW YORK — Democrats in races that will help determine control of the Senate are rapidly burning through their campaign cash, whittling away their financial advantage over Republican opponents as they fend off attacks from conservative groups, according to figures released through Friday.
The spending on both sides underscores the critical role that outside conservative groups are playing as Republicans try to retake the Senate. In state after state, organizations like Americans for Prosperity, the nonprofit linked to David and Charles Koch, have kept Democrats on the defensive with a barrage of negative ads while establishment-backed Republican candidates raise money and navigate their way through primaries.
In Alaska, the Democratic incumbent, Senator Mark Begich, spent about as much money as he raised during the first three months of the year, while Dan Sullivan, a GOP candidate and former state attorney general, increased his fund-raising and narrowed Begich’s advantage in cash on hand. In Montana, Senator John Walsh, a Democrat, spent almost three-quarters of the money he raised since January, ending with about $700,000. Representative Bruce Braley of Iowa, the likely Democratic nominee for Senate, spent more than 60 percent of the cash he raised.
Senator Mary L. Landrieu, Democrat of Louisiana, spent only about a third of what she collected through the end of March. But she reserved $2.7 million of advertising in March, according to strategists tracking both parties’ television spending, which will cut deeply into the $7.5 million she reported at the beginning of April.
“The spending totals so far show that a lot of Democratic candidates find themselves on the run,” said Brad Dayspring, a spokesman for the National Republican Senatorial Committee.
Democratic strategists say their candidates have faced a historic early onslaught of outside spending — about $33 million in all, most of it from Koch-linked groups — without squandering their coffers and while staying, for the most part, ahead of or even with their Republican rivals in the polls.
In the five battleground races where both candidates have reported their totals — Alaska, Montana, North Carolina, Colorado, and Louisiana — Democrats reported a combined $25.2 million in cash on hand, compared with $12.1 million for Republicans. The Democratic Senatorial Campaign Committee had $22 million more, compared with $15.9 million for the GOP committee.
“Up and down the map, Democrats are outpolling and out-fund-raising their Republican opponents, and we enjoy cash-on-hand advantages at both the campaign and committee level,” said Justin Barasky, a spokesman for the Democratic committee. “We feel very confident that, going forward, this will ensure Democrats have the resources we need to win in November.”
Democratic outside groups, which largely held their fire in the fall, have begun to increase their spending on behalf of Senate candidates while the party moves aggressively to tie Republican candidates to wealthy donors like the Kochs. According to media buyers, these Democratic groups spent about $4 million in March, led by Senate Majority PAC, a so-called super PAC with ties to the Democratic leader, Senator Harry Reid of Nevada. Republican groups spent about $5.5 million.
Several Republican challengers will need to spend more heavily in the weeks ahead to beat back rivals for the party’s nomination, or to introduce themselves to voters against Democrats who are already well-known.
In the Senate race in Kentucky, neither Mitch McConnell, the Republican leader, nor Alison Lundergan Grimes, his Democratic challenger, has released recent figures. But in the last six months, Grimes has narrowed the financial gap with McConnell, who faces a primary challenge and attacks from conservative groups. In Republican-leaning Georgia, which has an open Senate seat, the Democratic candidate, Michelle Nunn, posted consistently strong fund-raising numbers during the second half of last year.
And some Republican candidates are floundering in the hunt for cash.
Senator Kay Hagan of North Carolina, a Democrat who has been the subject of nearly ceaseless attack ads from conservative groups since the fall, conserved about half of the cash she raised and began the spring with $8.3 million in hand. Thom Tillis, a Republican, spent significantly more than he raised during the first three months of the year. Tillis, the speaker of the North Carolina House, began April with just $1 million in cash on hand and is locked in a primary fight.
In many general election matchups, spending by Republican super PACs and political nonprofit groups appears to have more than evened the financial playing field with Democrats.