TOPEKA — Gov. Jeff Colyer has a message for Republican voters as the primary campaign enters its final week: a vote for anyone but me is a vote for Kris Kobach.

Votes for other Republican candidates, such as former state senator Jim Barnett or Insurance Commissioner Ken Selzer, are effectively the same as a vote for Kobach, a Colyer TV ad says.

“Let’s be clear: Jeff Colyer is the only candidate that can beat Kris Kobach,” the Colyer TV ad says.

Republican opponents of Kobach, including Colyer, contend he wouldn’t be an effective leader and fear he would be a weak general election candidate. Kobach has said many of his signature issues, like stopping illegal immigration, appeal to most voters. He has called Colyer’s attacks a sign of desperation.

The Kansas Republican race for governor bears some similarities to the 2016 presidential race, when Donald Trump won the party’s nomination despite the efforts of a slew of candidates who tried to defeat him.

Colyer has promoted endorsements from several groups that hold sway in Republican politics, including the National Rifle Association and Kansas Farm Bureau. On Monday, Colyer’s campaign announced the endorsement of former U.S. Sen. Bob Dole.

Kobach is emphasizing his ties to Trump, including the endorsement of Donald Trump Jr., the president’s oldest son. Trump Jr. has recorded a robocall urging voters to back Kobach.

Kobach’s campaign also appears to be elevating other GOP candidates that might draw votes from Colyer. The Kobach campaign calls Barnett the obvious choice for moderate Republicans and says a new poll shows Selzer “on the move” with improving support heading toward Election Day.

Over the weekend, the Kobach campaign released a poll it paid for that shows him in the lead. But it also shows a majority of likely Republican voters remain undecided or support candidates other than Kobach.

That could work in the favor of either campaign. Kobach needs only to draw the most votes to win the primary. The flip side is that there is a large pool of voters who don’t support Kobach and could potentially be convinced to support Colyer instead.

“The Kobach poll backs up the Colyer ad ... Colyer’s own opponent’s poll is backing up Colyer’s strategy here,” said Bob Beatty, a political scientist at Washburn University.

Kobach spokeswoman Danedri Herbert said the poll shows why Colyer has launched “so many desperate, negative attacks” against Kobach. Colyer has said he is making clear what’s at stake in the race.

Meanwhile, some more moderate Republicans are wrestling with whether to vote for Colyer in an effort to stop Kobach or side with a candidate more aligned with their views, such as Barnett.

For others, it means making a calculated decision to vote for Colyer in the hope of stopping Kobach, said Brandi Fisher, director of the Mainstream Coalition, which aims to elect moderate candidates. The group has endorsed Barnett.

Still others are quietly supporting Kobach because they think he’ll be easier to beat in the general election, Fisher said. She said Mainstream does not support that approach.

“The challenge is even amongst like-minded people, there are all sorts of different calculations,” Fisher said.

For his part, Barnett says he is the only ideological alternative to Colyer, Kobach and Selzer, who are all more conservative than he.

“What the (Colyer TV) ad is implying is that there’s somebody better out there, and it’s Jim Barnett and Rosie Hansen,” Barnett said in an interview, referring to his wife and running mate.

In his own TV ad, Selzer warns voters not to think Colyer and Kobach are the only choices for governor. He says the two men are “peas in the pod” and part of a broken system.

“We understand why Jeff Colyer is releasing this ad. He knows that Selzer is rising significantly in the polls,” Selzer spokeswoman Lindsay Preisinger said.

The Kobach campaign didn’t immediately respond to a question about Colyer’s ad on Monday.

Although there are significant differences between a nationwide presidential contest with many elections and caucuses and a one-time statewide primary, there also are striking similarities.

In the 2016 Republican race for president, Trump won less than half of the Republican voters. As the primary season entered its final stretch, Texas Sen. Ted Cruz positioned himself as the only candidate capable of defeating Trump.

In Kansas, Kobach is the most Trump-like figure in race, with Colyer positioning himself as the only conservative candidate able to stop him.

“I have never liked the ‘anybody but fill in the blank’ argument -- in this case, anybody but Kobach. It doesn’t generally win,” said Michael Smith, a political scientist at Emporia State University. “My gut feeling is that voters have to vote for a candidate.”

Contributing: Mike Hendricks of The Kansas City Star