FILE: Sen. Joni Ernst (r-iOWA)  (Photo by Jonathan Newton / The Washington Post)

This post has been updated

DES MOINES -- Sen. Joni Ernst (R-Iowa) will attend a rally here in Iowa next week for presidential contender Sen. Marco Rubio (R-Fla.), as signs mount that the state's GOP establishment and elected officials are turning against Sen. Ted Cruz (R-Tex.).

Ernst said she doesn't plan to endorse, but will introduce Rubio at a rally here.

"Marco is not only a strong conservative and a good friend, but someone that I trust to secure our country," Ernst said in a statement. A number of Rubio's staffers worked on Ernst's 2014 Senate race. Cruz skipped a motorcycle ride Ernst hosted last year that many other Republican candidates attended. A spokeswoman for Ernst said she is willing to introduce any presidential candidate who asks her to do so if both can fit it into their schedules.

Ernst's announcement comes as Iowa's elected officials are increasingly lining up against Cruz, who is fighting for the top spot here with businessman Donald Trump. Sen. Chuck Grassley (R) attended a Trump event Saturday. While he did not endorse Trump, his presence showed increasing signs of cooperation between Trump and the Republican establishment.

Sen. Joni Ernst (R-Iowa) welcomes Sen. Marco Rubio (R-Fla.) at the Iowa GOP's Growth and Opportunity Party on Oct. 31. Louisiana Governor Bobby Jindal was also at the gathering and spoke to reporters about his take on the debates. (Sarah Parnass/The Washington Post)

[GOP establishment warms to Trump — and remains cool toward Cruz]

"I want Mr. Trump to know that I appreciate his support for me and most importantly for Iowa being first in the nation, our all important Iowa caucus,” Grassley told a crowd of about 500 in Pella, Iowa. “We’ve got to keep up this energy that’s shown here today and many other places around Iowa because that is what it’s going to take for us to win back the White House in November."

[With subtle Chuck Grassley embrace, signs of growing cooperation between Trump and GOP establishment]

When asked about Grassley, Cruz spoke about legislation the two have worked on together in the Senate.

Gov. Terry Branstad (R) last week said he wants to see Cruz lose the caucuses.

"I think it would be a big mistake for Iowa to support him," Branstad said of Cruz last week. Branstad has also questioned whether Cruz, who was born in Canada, is eligible to run for president.

[Iowa’s governor wants Ted Cruz to lose the caucuses. Cruz says the GOP establishment is in a panic.]

The Texas Republican takes this all as a positive sign - he said last week Branstad's broadside shows that the establishment is scared of his candidacy.

"It is no surprise that the establishment is in full panic mode," Cruz said. "As conservatives unite behind our campaign, we are going to see the Washington cartel firing every shot they can, every cannon they can, because the Washington cartel lives on cronyism. It lives on making deals."

"We will see like ‘The Empire Strikes back,’ the establishment will strike back because they don’t want an end to the cronyism and the gravy train from Washington," he said.

As the establishment increasingly lines up behind Trump, Cruz is seeking to paint the businessman as a part of what he calls the "Washington cartel," politicians who are willing to do whatever it takes to advance their mutual interests.