Former Florida Governor Jeb Bush is expected to formally announce his campaign for the Republican presidential nomination on June 15 in Miami, according to a new campaign website that went live early Thursday.

"Coming soon ...," Bush said on his Twitter account, linking to the website. A companion message was posted in Spanish.

Bush, the son of former president George H.W. Bush and brother of former president George W. Bush, is entering a crowded field of Republican candidates ahead of the November 2016 presidential election, with former Texas Governor Rick Perry the latest to join.

Bush, 62, has been raising money and campaigning for months, but not as an official candidate.

Watchdog groups are asking the Justice Department to investigate him and others for possibly using his "non candidacy" to skirt federal election fundraising laws. Bush's spokeswoman said, in response to questions about his fundraising, that he is fully complying with the law.

With an announcement, he would immediately become one of the top-tier candidates for the nomination. As the candidate who most represents the establishment wing of the party, he already leads many national polls of Republicans who are considering a wide-open field for the 2016 nomination.

His main challenge is to convince conservative Republicans to set aside concerns he is too moderate, even as he tries to expand the reach of Republicans who have lost the last two presidential elections and are seen as facing an uphill battle in 2016.

The pressure will be on to show how he is different from fresher faces in the party like Wisconsin Governor Scott Walker and Florida Senator Marco Rubio. Both he and Rubio are from Florida.

One issue that may give him trouble with conservatives is his more welcoming attitude toward illegal immigrants. He has geared his candidacy toward making himself more appealing to Hispanic-Americans, a voting bloc growing in significance, particularly in key swing states like Nevada, Colorado and his home state of Florida.