(For factbox on Republicans seen as potential candidates for their party's nomination in 2012, click on [ID:nN03184162]

* Political world stunned by Palin resignation

* Palin had been subjected to widespread ridicule

* Alaska Republican senator says Palin "abandoned" state (Adds Murkowski statement, paragraphs 5-6)

By Steve Holland

WASHINGTON, July 4 (Reuters) - Republican Senator John McCain expressed support for his former presidential running mate, Sarah Palin, on Saturday as Washington speculated about why the Alaska governor abruptly announced her resignation.

McCain made the comment a day after Palin stunned the political world by announcing she is stepping down with 18 months left in her term.

McCain had plucked Palin from obscurity to make her his vice presidential running mate in last year's presidential campaign won by Democrat Barack Obama.

"I have the greatest respect and affection for Sarah, Todd, and their family. I was deeply honored to have her as my running mate and believe she will continue to play an important leadership role in the Republican Party and our nation," McCain said in a statement e-mailed to Reuters.