Senate Democrats’ campaign committee on Thursday began canceling plans for television ads in Louisiana’s major markets to help U.S. Sen. Mary Landrieu’s runoff campaign against Republican Congressman Bill Cassidy, making her re-election bid an even steeper challenge.

The Democratic Senatorial Campaign Committee initially had reserved $1.8 million in television advertising for after Tuesday’s first round of voting. On Thursday, the committee dumped the bookings in the state’s big cities.

A spokesman for the debt-laden committee said officials still back Landrieu, who has twice before prevailed during runoff elections, and would keep an eye on the race.

“Mary Landrieu is a proven runoff winner, and we support her 100 percent,” DSCC spokesman Justin Barasky said. “We are going to make ongoing determinations on how best to invest in the race.”

Tuesday’s midterm elections swept Republicans into a Senate majority for the first time since 2006. That takes away Landrieu’s chairmanship of the vaunted energy committee and undermines her main argument for re-election — clout — as she and Cassidy head into a new round of campaigning ahead of the Dec. 6 runoff.

Landrieu pitched herself to constituents as a powerful force on Capitol Hill and an ally to Louisiana’s energy workers. Oil and gas producers helped fund her campaign. And she was seen as playing a crucial role in Democrats’ strategy to retain the majority.

Those sources of support seemed ready to dry up as Landrieu campaigned in a runoff, which was required because no candidate got 50 percent of the vote in Tuesday’s elections.

“She has no juice on Capitol Hill now,” National Republican Senatorial Committee communications adviser Kevin McLaughlin said Thursday. “She’s now a rank-and-file member.”

“While the Democratic Senatorial Campaign Committee recalibrates, our campaign for Louisiana’s future still has a lot of juice, a lot of heart, and, most importantly, a strong and positive record to run on. Our campaign has never been about money or the party, but fighting for the people of Louisiana and delivering for them time and time again, despite the gridlock in Washington,” Fabien Levy, the Landrieu campaign communications director, said in a prepared statement. “We have the passion and energy necessary for victory on December 6, and are confident we will have the necessary resources from Louisiana voters to win.”

The two candidates launched their runoff campaigns Wednesday, with Landrieu continuing on a sort of Cassidy-bashing tour of the state on Thursday.

Cassidy, meanwhile, attended an anti-abortion event slamming Landrieu for her support of abortion rights. He agreed to participate in one of the six debates Landrieu had proposed — on Dec. 1 — but threw in a twist: Cassidy said he’d agree to another debate date for every time Landrieu campaigns in Louisiana with President Barack Obama.

The Senate Republicans’ campaign arm booked $2.8 million in ads weeks ago. The early booking gave Republicans discounted rates on airtime. Landrieu refused to book post-Nov. 4 airtime, and she now faces higher costs to get on the air for her monthlong runoff.

A meaningful advertising buy in Louisiana needs at least $500,000 a week behind it, campaign buyers said.

As of Oct. 15, Cassidy had $3.1 million banked to Landrieu’s $1.6 million, according to campaign finance reports.

Outsiders were set to have great sway, both in their actions and their inaction.

The Koch-backed Freedom Partners Action Fund rushed to the airwaves on Wednesday, starting a more than $2 million ad blitz to criticize Landrieu. The Karl Rove-backed American Crossroads network planned to keep throwing cash at the race, too, having spent $2 million ahead of Tuesday’s first round of voting.

At the same time, Democrats’ largest super PAC, Senate Majority PAC, had not booked airtime for the runoff. Another of its major players, NextGen Climate Action, backed candidates who pledged to defend the environment; Landrieu’s positions did not win her many fans among NextGen donors or advisers.

And the DSCC already was at least $10 million in the red for campaign costs, and a Democratic victory in Louisiana would not reverse the Republican tide that tipped the Senate in its favor. Separately, the committee had about $5 million in debt for the purchase of a headquarters earlier this year.

The NRSC, too, was about $9 million in debt. But the party in power typically has an easier time paying down its debt. And the newly elected Republicans were expected to help the party pay off that debt.

More than $30 million in advertising had been aired so far, but Republicans all but dropped their ads in recent weeks to save cash. Democrats stayed on the air, unsuccessfully trying to dodge a runoff.