Gov. Scott Walker endorsed Ted Cruz for president Tuesday, reinforcing his opposition to Donald Trump a week before Wisconsin’s primary.

The GOP governor dropped out of the race for president in September amid fundraising and polling woes. At the time, he cited the need to stop Trump as his reason for quitting.

Walker announced his backing of Cruz — and said he would campaign with him in the coming days — in an interview with conservative talk show host Charlie Sykes on WTMJ-AM (620). Sykes is a vocal Trump critic who had a feisty exchange with the New York real estate titan on Monday.

“We need a leader in Washington who understands that our founders intended for the power really to be in the state and really in the hands of the people, not concentrated in Washington,” Walker said. “Ted Cruz not only believes that, he’s shown he’s willing to act on that.

“He has shown he is not afraid to take on the big government special interests.”

On Monday, Trump posted a message on Twitter making clear he didn’t expect to get Walker’s endorsement.

“After the way I beat Gov. Scott Walker (and Jeb, Rand, Marco and all others) in the presidential primaries, no way he would ever endorse me!” Trump said in his tweet, referring to former Florida Gov. Jeb Bush, Sen. Rand Paul of Kentucky and Sen. Marco Rubio of Florida.

Walker’s support for Cruz comes at a time when the freshman senator from Texas is trying to catch up in delegates with Trump. Ohio Gov. John Kasich is also seeking the Republican nomination.

Cruz made a stop in Brookfield on Tuesday, and crowd listened to Walker’s endorsement before Cruz took the stage.

“He stays firm, he sticks to his guns,” Walker said of Cruz. “He’s been pushed many times over, not only by the left, but sometimes even by those in his same party, but he stayed true to who he is and what he believes in and I think that will go over very, very well.”

Walker predicted Cruz would win Wisconsin and go on to secure the 1,237 delegates needed to win the nomination outright, avoiding a contested convention in July.

Walker’s favorability rating has lurked in the high 30s with the general population since he dropped out of the presidential contest, but he remains popular among Republicans.

He didn’t name Trump when he left the presidential race, but made clear then that he didn’t want him as the nominee. He said at the time he was “helping to clear the field” and hoped others would do the same “so that the voters can focus on a limited number of candidates who can offer a positive conservative alternative to the current front-runner.”

Last summer, Trump attacked Walker, saying “Wisconsin is doing terribly” under him, citing problems with the state budget.

The two have also gotten along in the past. Trump donated $10,000 — the maximum allowed under the law at the time — to Walker’s re-election bid in 2014. Also, court records show Trump gave $15,000 to the conservative Wisconsin Club for Growth soon after Walker’s team discussed urging him and other millionaires and billionaires to donate to the group to fight recall efforts against Wisconsin Republicans.

Walker said during his presidential run that he would support the eventual nominee. He noted he’d done that when asked last month if he would support Trump if he is chosen as the nominee.

Wisconsin is the only state with a primary on April 5, and the candidates are camping out in the Badger State.

In addition to his stop in Brookfield, Cruz is visting Cedarburg Tuesday, while Trump will be in Janesville, the hometown of House Speaker Paul Ryan, who has admonished Trump for the tone of the presidential race.

Kasich will be in Waukesha, and all three Republican candidates will participate in a CNN forum in Milwaukee.

On the Democratic side, former Secretary of State Hillary Clinton will visit Milwaukee, La Crosse and Green Bay. U.S. Sen. Bernie Sanders is hitting Appleton and West Allis.

David Paulsen of the Journal Sentinel staff contributed to this report.