Wisconsin Gov. Scott Walker announced Monday evening that he is suspending his campaign for the Republican presidential nomination in 2016.

At a press conference in Madison, Wis., Walker said the Republican race is more focused on personal attacks than it is on fixing real issues facing the country.

“I believe that I am being called to lead by helping to clear the race so that a positive conservative message can rise to the top of the field,” Walker said.

He also encouraged other candidates in the race to do the same, so that the GOP could rally around other candidates.

“I encourage other Republican presidential candidates to consider doing the same so the voters can focus on a limited number of candidates who can offer a positive conservative alternative to the current frontrunner,” Walker said.

Walker, who once held a commanding lead in Iowa after a fiery speech earlier this year, has struggled in recent weeks, both in Iowa and nationally. 

Walker began to attract support following a speech at Congressman Steve King’s “Iowa Freedom Summit” in January, and polling throughout the year showed him with double-digit leads. In several polls, Walker had support from 25 percent of likely caucus goers.

Walker committed to traveling to all of Iowa’s 99 counties once his campaigned caught on in Iowa. His first stop after announcing his candidacy was in the Quad Cities and he made dozens of stops around the state in the following weeks.

A new national CNN/ORC poll released Sunday showed Walker with less than 1 percent support from Republican voters. Recent Iowa polls showed Republican frontrunner Donald Trump in double digits, while Walker was stuck at about 5 percent support.

“Sort of a snide remark is he got ‘Trumped,’ and pretty much everybody else [has throughout the race],” said Mack Shelley, an ISU professor of political science. “I think that’s literally part of the answer, that the Donald took all the air out of the room and ended up stealing a whole lot of talking points that conservatives would have had going for them.”

Shelley also said Walker’s performance in the first two Republican debates did not live up to expectations, and that other candidates on stage had a much more visible presence. 

Walker was in Iowa as recently as Sunday, campaigning around the state. He appeared at a gathering with seven other Republican candidates in Des Moines this weekend, as well.

Other Republican’s still in the race offered praise for Walker following his announcement: 

I got to know @ScottWalker well—he’s a very nice person and has a great future.

— Donald J. Trump (@realDonaldTrump) September 21, 2015

.@ScottWalker is a good man who entered the presidential race after winning three grueling campaigns in four years.

— Marco Rubio (@marcorubio) September 21, 2015

I wish @ScottWalker all the best in his future endeavors. I believe Governor Walker will remain a vital voice in the Republican Party.

— Dr. Rand Paul (@RandPaul) September 21, 2015

I wish Gov. @ScottWalker and Tonette all the best in their continued service to Wisconsin and the country: https://t.co/vMLbZyvTDj

— Ted Cruz (@tedcruz) September 21, 2015

Make no mistake, a strong leader like @ScottWalker has a bright future & is a model for other governors. Good luck, Scott! -John

— John Kasich (@JohnKasich) September 21, 2015

Scott Walker is a good man who has a proven record of fighting for conservative reforms. I know he’ll continue to do that as Governor.

— Jeb Bush (@JebBush) September 21, 2015

@ScottWalker has been one of US’ strongest governors. People of WI are blessed to have his leadership. Not the last we’ve heard of him!

— Rick Santorum (@RickSantorum) September 21, 2015

I wish @ScottWalker all the best. He’s a great Governor, a fighter & a good friend. I know he will continue to work hard for our party & WI.

— Chris Christie (@ChrisChristie) September 21, 2015

Walker is the second candidate to drop out of the race, following Texas Gov. Rick Perry suspending his campaign on Sept. 11. 15 other major candidates remain on the Republican side.