(AP) - Barack Obama readied his announcement by text message Friday of his vice presidential running mate from a list suddenly spiced by a dark horse from Texas.

The prospect of Sen. Hillary Clinton (D-N.Y.) being chosen remained a mystery on a day full of them, although senior aides said the Obama campaign had never requested financial or other records from her.

Three days before the party gathers in Denver to nominate Obama for the fall campaign, several officials said Rep. Chet Edwards, whose district includes President Bush's ranch in Crawford, Texas, had made the roster of potential running mates. Senators Joe Biden, of Delaware, and Evan Bayh, of Indiana, were also in the mix, as were governors Tim Kaine, of Virginia, and Kathleen Sebelius, of Kansas, ? and any unknown others Obama had managed to keep secret despite intense scrutiny.

"It'll be exciting news," Sebelius told reporters in Kansas.

Obama went to the gym for a morning workout before heading to an office in Chicago to polish the convention acceptance speech he will deliver next Thursday night.

Obama told reporters Thursday he's already made his choice, and aides have used the prospect of a text-message announcement to try to attract additional supporters by soliciting their cell phone numbers and e-mail addresses.

The Illinois senator has arranged a joint appearance for Saturday with his running mate at the Old State Capitol in Springfield, Ill.

Among those believed in the running, Biden, Bayh and Edwards fit the mold of a running mate with experience in defense or foreign policy - areas in which Obama performs relatively poorly in the polls compared with his opponent, Sen. John McCain (R-Ariz.).

Clinton's credentials were forged in the primaries and caucuses where she ran a close second to Obama in the battle for the nomination.

Edwards, whom House Speaker Nancy Pelosi (D-Calif.) had touted as a running mate, told The Associated Press in Waco, Texas, "I have had interactions with the Obama campaign over the last several months but I will not get into details."

Edwards, chairman of the Military Construction and Veterans Affairs Appropriations Subcommittee, is a nine-term moderate Democrat representing the GOP-leaning Texas district. He is well-known in Texas but does not have a national profile.