Topeka, Kan. — One of four Kansas legislators who made headlines last year by defecting from the Republican Party is running for the U.S. Senate as a "pragmatic" Democrat, entering a race in which some GOP leaders are worried about immigration hardliner Kris Kobach 's chances should he win their party's nomination.

State Senator Barbara Bollier, a retired suburban Kansas City anesthesiologist, launched her bid Wednesday, a day after campaign finance reports showed that Kobach is well behind a GOP rival, U.S. Rep. Roger Marshall, in fundraising. Marshall, who represents western Kansas in Congress, raised twice as much in contributions as Kobach from July 1 through Sept. 30 and ended the period with nearly $1.9 million in cash, compared to about $198,000 for Kobach.

Kobach, the former Kansas secretary of state, lost last year's governor's race to Democrat Laura Kelly, and some Republicans have complained that his fundraising was lackluster. His take-no-prisoners style of conservatism also alienated many GOP moderates, and Democrats see his nomination as their best chance to win their first Senate race in Kansas since 1932.

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Bollier, 61, was first elected to the Legislature in 2010 as a Republican but quickly found herself at odds with the party's conservative leaders on fiscal matters and social issues such as abortion and LGBTQ rights. She endorsed Kelly in the governor's race and was stripped of a committee vice chairmanship, then switched parties in December, the first of four moderate GOP lawmakers to do so in a week.

She opened her campaign with an announcement video promising to be a "voice of reason" in Washington, just as Kelly described herself in her race against Kobach as a centrist who could work with members of both parties to solve problems. Bollier also emphasized her career as a doctor.

"The truth is, as a doctor, I've never really been about partisan labels, just problem solving. And we need more of that right now," Bollier said in her video.

Bollier joins an already crowded race for the seat held by Republican Senator Pat Roberts, who isn't seeking a fifth term. Kobach, the former Kansas secretary of state, has built a national profile by advocating for tough policies against illegal immigration.

FILE: President-elect Donald Trump pauses pose for photographs as he greets Kansas Secretary of State, Kris Kobach, at the Trump National Golf Club Bedminster clubhouse, Sunday, Nov. 20, 2016, in Bedminster, N.J. Carolyn Kaster, AP

Besides Kobach and Marshall, other GOP candidates include Kansas Senate President Susan Wagle, of Wichita, and Dave Lindstrom, a Kansas City-area businessman and former Kansas City Chiefs player.

Former federal prosecutor Barry Grissom and Manhattan Mayor Pro Tem Usha Reddi also are seeking the Democratic nomination.

Grissom's latest campaign finance report showed that he raised nearly $469,000 during the last quarter and ended September with $366,000 in cash. Reddi raised about $61,000 and ended the period with about $54,000.

Top Democrats wouldn't describe Bollier as the front-runner Wednesday. But Kansas House Minority Leader Tom Sawyer said, "If she is the nominee, she does have a good shot of picking up those moderate Republicans that we need to win in a general election."

Some Republicans' fears that Kobach would emerge from a crowded primary — just as he did in the governor's race — led to an effort to encourage U.S. Secretary of State Mike Pompeo to jump into the race. So far, Pompeo has been coy, prompting Marshall and the others to run.

U.S. Rep. Roger Marshall, R.-Kan., speaks to an Associated Press reporter outside an RV he uses in traveling the state. John Hanna / AP

Marshall began with a big fundraising advantage, the ability to transfer $1.4 million from his House campaign. He then raised more than $572,000 in contributions during the last quarter, outpacing the other candidates.

Kobach trailed Marshall in fundraising, even with events featuring billionaire investor Peter Thiel, conservative commentator Ann Coulter and former White House aide Steve Bannon.

He finished behind Wagle and Lindstrom in campaign cash on hand at the end of September, but both of them made big loans to their campaigns.

Wagle raised nearly $248,000 and loaned her campaign $275,000, ending the period with almost $495,000. Lindstrom raised about $151,000 and loaned himself $100,000, finishing the period with about $241,000.

Kobach raised about $250,000 during the quarter, and his campaign said it hit its fundraising goal. It also bragged that he had more than 1,300 donors.

"I'll take a huge number of contributors over a huge dollar amount any day of the week," Kobach said in a statement.