WASHINGTON (Reuters) - Rick Santorum and Marco Rubio are the top two choices among Republican voters as Mitt Romney's vice presidential running mate, according to a Reuters/Ipsos poll released on Thursday.

Eighteen percent of registered Republican voters picked former Pennsylvania Senator Santorum out of a list of 19 potential running mates for Romney, the party's presumptive presidential nominee to face President Barack Obama in a November 6 election.

Seventeen percent chose Rubio, a U.S. senator from Florida. Rubio was also the most popular pick among members of the Tea Party movement, a group that Romney wants to win over as he works to solidify his support among the party's conservatives after a divisive primary fight.

Twenty-three percent of Tea Party members picked Rubio in the online poll, compared with 16-percent support among the group for Santorum, who ended his own presidential run last month.

(Reporting By Patricia Zengerle; Editing by Eric Beech)