Washington, May 4 (IANS): Democratic hopeful Bernie Sanders picked up a key win in Tuesday night's Indiana state primary and is confident he can keep winning in the upcoming contests in West Virginia, Kentucky and Oregon.

The Vermont senator led the Indiana polls with 53 percent against party front-runner Hillary Clinton who had 48 percent of the total votes, Politico reported.

Less than a half hour after results began pouring in, Sanders rallied supporters in Louisville, Kentucky, where voters will head to the polls on May 17.

Ticking through his standard stump lines while bashing Clinton for her paid speeches and 2002 vote in favour of invading Iraq, Sanders told a boisterous crowd that their ideas will prevail.

“I’ll tell you what is extremely exciting for me, and that is that in primary after primary, caucus after caucus, we end up winning the vote of people 45 years of age and younger,” Sanders said, adding “And that is important because it tells me that ideas that we are fighting for are the ideas for the future of America and the future of the Democratic Party.”

According to experts, the calendar for the rest of May portends favorably for Sanders, as well, with West Virginia up next on May 10, followed by Kentucky and Oregon on May 17.

“I want to thank the people of Indiana for the great upset victory that they gave us tonight. This is the 18th state that we have won, and we expect more victories in the weeks to come," Sanders said in a statement released Tuesday night.

With 83 pledged delegates at stake, Indiana loomed large as an opportunity for Sanders to pull an upset in a state where Clinton has led narrowly in most recent polls. A joint NBC News, Wall Street Journal and Marist College survey conducted last week showed her with a 4-point lead.

Sanders had kept up his criticism of the Democratic nomination process, riffing to crowds across Indiana on Monday about the outsize role superdelegates play and vowing to fight for a contested nomination should Clinton need those superdelegates to put her over the total number of 2,383 need to win.

Clinton still leads the Democrats race with 2,217 votes (pledged: 1704, superdelegates: 513) against Sanders who has a total of 1443 votes (pledged: 1402, superdelegates: 41), according to CNN figures.

Sanders have vowed to keep up the fight to clinch the final nomination, and said his ongoing struggle with Clinton would help the party in the fall.

“The Clinton campaign thinks this is over. They’re wrong,” Sanders said. "Maybe it’s over for the insiders and the party establishment, but the voters in Indiana had a different idea. The campaign wasn’t over for them. It isn’t over for the voters in West Virginia. It isn’t over for Democrats in Oregon, New Jersey and Kentucky. It isn’t over for voters in California and all the other states with contests still to come."