Story highlights Marco Rubio refused to say in an interview with CNN if he'd back Cruz

One GOP senator may endorse Cruz: Steve Daines of Montana

Washington (CNN) GOP senators on Wednesday are not showing any rush to back Texas Sen. Ted Cruz after his big win in Wisconsin.

Most are staying mum, plan to be neutral to avoid angering Donald Trump supporters back home or say Cruz needs to do more outreach to win over GOP senators whom he has dubbed as part of the "Washington cartel."

It's a reminder that many Republican establishment senators are still uncomfortable with the Texas senator despite their fear of Trump, the party's presidential front-runner.

Sen. Marco Rubio refused to say in an interview with CNN if he'd back Cruz.

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