FACTBOX: Scenarios for McCain VP pick Sarah Palin

(Reuters) - Republican presidential candidate John McCain's newly chosen running mate, Alaska Gov. Sarah Palin, created an immediate stir with news that she is the subject of a state ethics probe and her unmarried teenage daughter is pregnant.

Palin will accept the nomination on Wednesday in a speech to the Republican convention. Here are some potential scenarios for her candidacy and its impact on the November 4 presidential election against Democratic presidential candidate Barack Obama and his No. 2, Joe Biden.

- The choice of Palin, 44, a conservative abortion rights opponent with a record of bucking the Republican establishment in Alaska, has rallied the conservative base to McCain, who has struggled to win over that crucial constituency.

Her speech will give the party a chance to answer questions about her familiarity with domestic and foreign policy issues, and possibly address the issue of her 17-year-old daughter's pregnancy and the investigation into whether she abused her power in having a public safety commissioner fired in Alaska.

"She'll be greeted rapturously because the delegates are very conservative, as is she," University of Virginia political analyst Larry Sabato said of her convention appearance. "She's become their heroine. But what the delegates think and what the country thinks are probably two different things."

- The selection of the political unknown has raised questions about McCain's judgment and the degree to which his campaign investigated Palin's background. That is a distraction that could hurt the campaign's efforts to generate momentum for the election battle with Obama.

"My vetting process was completely thorough and I'm grateful for the results," McCain told reporters in Philadelphia.

- Palin's slot on the ticket is secure, but new revelations or scandals from Alaska could threaten her standing. It would take a lot, however, to dump her two months before the election.

"If he drops her, the election is over. There's zero chance that he'll drop her," Sabato said.

(Writing by John Whitesides, editing by Jackie Frank)