A spokeswoman says Pennsylvania's freshman U.S. Sen. Pat Toomey isn't endorsing anyone in the GOP presidential campaign.
In a Twitter dispatch from his official account, Toomey said Thursday that Romney's tax reform plan is strong and “very much like” his own.
Toomey was responding to campaign developments the day before. Romney issued details of his tax plan and criticized Santorum for endorsing Arlen Specter in Specter's successful bid to beat back Toomey's primary challenge.
Specter later switched to the Democratic Party and voted for President Barack Obama's health care overhaul and economic stimulus bills.
Toomey won Specter's seat in 2010, and supporters say he'd make a good vice president.
The Pa. primary is set for April 24.