It’s Act Two in the GOP veepstakes drama.

Sen. John Thune (R-S.D.). (AP Photo/Charles Dharapak)

Thune, a rising star who serves in the No. 3 spot in Senate Republican leadership, will hold a meet-and-greet with Colorado Republicans Saturday morning in Denver and will address the state GOP convention.

Colorado has already held its GOP presidential caucuses – former senator Rick Santorum won them back in February, taking 40 percent to Romney’s 35 percent. But the statewide convention is an important gathering of the Colorado GOP’s activist base, a constituency that Romney will have to woo if he wants to bring the state back into the Republican column come November.

Thune’s visit on Romney’s behalf comes on the heels of a campaign trail appearance by another potential Romney running mate, Sen. Rob Portman. The Ohio Republican stumped for Romney in Pennsylvania last weekend.

Thune is not quite in the top tier of potential VP picks, however; our colleagues at The Fix rank him as No. 7 on their veepstakes rundown, just behind New Jersey Gov. Chris Christie (R).