A week after his surprising victory in Michigan's primary, Democratic presidential candidate Bernie Sanders is predicting his next big wins.

The Vermont senator told more than 2,000 supporters crammed into a St. Louis high school gymnasium during a March 13 rally to prepare for a repeat of Michigan.

Delegates from five important states are up for grabs Tuesday. Sanders is hopeful that he could win as many as three of those states -- Missouri, Illinois and Ohio.

His opponent, Hillary Clinton, has led Sanders in polling and has won more primary victories. But the race is by no means decided.

Clinton was expected to win Michigan's Democratic primary on March 8.

But Sanders was ultimately declared the winner in the race, securing about 18,000 more votes than Clinton.

Related: How Bernie Sanders beat Hillary Clinton in Michigan primary

That victory earned him 67 of Michigan's 127 delegates, pushing him that much closer to an opponent who many predicted would win hands down.

Sanders has already walked away with primary victories in nine states. With 553 pledged delegates, he is close behind Clinton, who has won 767 pledged delegates thus far.

But when you count the superdelegates, the vast majority of which have pledged support for Clinton, the former Secretary of State leads 1,234 to Sanders' 579.

One of those superdelegates pledged for Clinton is U.S. Rep. Dan Kildee, D-Flint Township.

Related: Congressman Dan Kildee maintains superdelegate pledge for Hillary Clinton

The list of 717 unpledged delegates, also called superdelegates, includes 20 "distinguished party leaders," 21 Democratic governors, 46 Democratic members of the U.S. Senate, 193 Democratic members of the U.S. House of Representatives and 435 elected members of the Democratic National Committee.

The unpledged delegates can decide who to support for the nomination and are not allocated according to state primary results like the about 4,768 pledged delegates.

Polling has favored Clinton in the race, though two recent polls have predicted narrow Sanders victories in the Missouri and Illinois primaries.

The two states both hold their primaries on Tuesday, March 15, as does Florida, North Carolina and Ohio. As the third straight Tuesday with several state primaries, it's being dubbed "Super Tuesday 3."

Meanwhile, Republican voters also go to the polls today as frontrunner Donald Trump hopes to widen his lead. The closest contest may be in Ohio where some polls have shown Gov. John Kasich with a slight lead over Trump.

Mark Tower covers government and politics for MLive. Contact him at 989-284-4807, by email at mtower@mlive.com or follow him on Twitter, Facebook or Google+.