Democratic Sen. Jon Tester backs GOP-championed Laken Riley Act

Montana Democratic Sen. Jon Tester continued his efforts to distinguish himself as a border security hard-liner on Thursday by becoming the first Senate Democrat to back an immigration bill that has been championed by Republicans in both chambers of Congress.

On Thursday afternoon, Tester announced his intention to co-sponsor the Laken Riley Act, a bill named after a 22-year-old nursing student who was killed while out on a run near the University of Georgia campus in February. Authorities say her alleged perpetrator is an undocumented migrant who was previously arrested for a non-violent crime but released by the New York Police Department.

The Laken Riley Act would require federal officials to apprehend and detain undocumented immigrants who commit crimes such as burglary, shoplifting or larceny until these individuals are removed from the United States.

The bill cleared the House in early March with support of every Republican and 37 Democrats.

But it hasn't gotten as robust support from Democrats in the upper chamber this time around.

The Senate previously considered the Laken Riley Act when Senate Republicans forced a vote on it as an amendment to a sweeping government funding package in March. The amendment was considered as a government shutdown loomed, and changes to the bill would have likely forced a government shutdown.

Tester voted in lockstep with his Democratic colleagues at the time and rejected the bill he's now co-sponsoring, though a spokesperson for his office told a local outlet at the time that he would have supported the legislation if it came to the floor as a stand-alone measure.Tim Sheehy, who is running against Tester, on Thursday accused him of doing a "flip-flop" on the act for political purposes.

Tester became the first Senate Democratic co-sponsor of the legislation on Thursday, joining a slate of GOP co-sponsors. The move comes as the Montana Democrat, who faces a tough reelection this November, looks to further establish himself as a border security hard-liner.

"Keeping Montana safe is my top priority, which is why I've repeatedly called on the Biden Administration and Congress to do more to secure the southern border and have worked to get the brave men and women in law enforcement what they need to keep criminals off our streets," Tester said in a statement. "After hearing from law enforcement officers across Montana, I'm backing the Laken Riley Act to make sure that individuals who enter our country and commit a crime are held accountable so that no Montana family has to worry about the safety of their loved ones."

Tester faces reelection in his deep-red state, where likely Republican Senate nominee Sheehy is working to make high numbers of unauthorized border crossings and the spread of fentanyl top issues for his campaign.

In recent months, Tester has become more and more outspoken about the challenges at the southern border.

Tester was closely watched during an effort by House Republicans to convict Department of Homeland Security Secretary Alejandro Mayorkas during a quickly-dispensed-with impeachment trial.

Though Tester did ultimately vote with his party to prevent a trial, he called the situation at the southern border "completely unacceptable" and said that the Biden administration needed to "do more" to keep the county safe.

Though there was an effort earlier this year to advance the bipartisan border security bill drafted by Sens. Chris Murphy, D-Ct., Kyrsten Sinema, I-Ariz., and James Lankford, R-Okla., those efforts ultimately stalled out after Senate Republicans rejected the deal because they felt it was not strong enough.

Senate Democrats, led by Majority Leader Chuck Schumer and Murphy, said yesterday they hope to reopen discussion about the border security provisions, just as sources tell ABC News that DHS is slated to propose a change to the process for those seeking asylum.

ABC News' Tal Axelrod contributed to this report.

Editor's note: This story has been updated to include that when the Senate previously considered the Laken Riley Act in March, Tester voted against it, and adds comments from Tester's Senate opponent, Tim Sheehy.