Former Pennsylvania senator Rick Santorum has formally launched a "testing the waters" account to consider a 2016 presidential bid.

The move, which his campaign confirmed to CBS News, marks the Pennsylvania Republican’s firmest step yet toward launching a bid for the GOP presidential nomination. A campaign spokesman told CBS that Santorum, who ran for president in the 2012 election, set up the account sometime this week.

Under Federal Election Commission guidelines, politicians in the "testing the waters" stage cannot engage in full-out campaigning but can begin raising and spending money on polling and travel. While the donations received do not have to be reported, they will eventually count toward the legal limits placed on campaign accounts by the FEC if the candidate launches a full-fledged campaign.

Sen. Rand Paul and Sen. Ted Cruz both formally declared their runs in recent weeks. Meanwhile, former Florida governor Jeb Bush and Wisconsin Governor Scott Walker have both been traveling and fundraising through their own political action committees, without officially launching campaigns.

Sen. Lindsay Graham (S.C.) is the only other candidate who has formally announced he is “testing the waters" but businessman Donald Trump and former neurosurgeon Ben Carson have both created exploratory committees.