She's 5-foot-4, favors fuchsia suits and isn't running in the British election.

But make no mistake: Nicola Sturgeon is the biggest thing in U.K. politics right now.

The leader of the Scottish National Party is likely to be the kingmaker after the May 7 vote, as opinion polls suggest neither major party will win an outright victory. She offered this month to join forces with the Labour Party to end austerity and help the poor. Conservative Prime Minister David Cameron says such an alliance would be "hell" for the economy.

With impressive performances in two nationally televised debates, Sturgeon has thrust herself into the forefront of the race — the woman whose party is in everyone's sights. And she's done it by being straightforward, positive and — for much of the British public — simply new.

"It is a phenomenon," said Ben Page of the Ipsos-MORI polling agency. "She's doing all the things that you aren't supposed to do in politics and it seems to be working for her."

The daughter of an electrician and a dental nurse, Sturgeon, 44, is a lawyer who trained at the University of Glasgow, in contrast to the Oxford and Cambridge elite that dominates British politics. She became leader of the SNP and Scotland's first minister in November after the party lost a hard-fought referendum on independence from the United Kingdom. Sturgeon's mentor, Alex Salmond, resigned after the failed campaign.

According to her biographer, Sturgeon made a conscious decision to soften her image and distance herself from Salmond's "street fighter" image. After she was sworn in as first minister, Sturgeon issued a press release saying she wore a dress by a designer from her hometown, calculating that such things are news in the modern world, said David Torrance, author of "Nicola Sturgeon, a Political Life."

People, especially those in the "media village," were expecting a female Salmond. Instead they saw an "impeccably turned-out, formidably articulate woman who exudes moderation," Torrance said. "It took them by surprise."

More than three decades after former Prime Minister Margaret Thatcher stepped down, Sturgeon remains a rarity in Britain — a woman in a top political office.

"She just appears like an ordinary, successful woman in a world full of dark-suited politicians who sound like politicians," said Murray Pittock, author of "The Road to Independence? Scotland Since the Sixties" and a professor at the University of Glasgow. "Fewer people are underestimating her now than four weeks ago."

It is the failed independence referendum that has made the SNP the linchpin of the general election.

SNP membership soared above 100,000 last month, from 25,000 two years ago, as the party signed up people who were engaged by the debate over independence. Though independence supporters fell short, their frustrations with politics as usual remained.

While Scotland is a traditional Labour stronghold, many Scots are angry with the party for allying itself too closely with the Tories during the independence referendum, and for not taking steps to ensure that promises made to them during the race were honored.

As a result, Labour is facing a cataclysm in Scotland, with some polls suggesting that the SNP may win as many as 55 of Scotland's 59 seats in Parliament next month. The SNP currently holds six seats and Labour 41.

Sturgeon is promising to end painful austerity measures and implement progressive policies to lift up the poor — a message that plays well in a country where real wages are still below the level they reached before the 2008 financial crisis.

"So to everyone who, like me, wants this election to herald the real and positive change that will make life better for ordinary people across these islands, I hold out a hand of friendship," she said Monday as she released a list of her party's policy priorities. "The SNP — if we are given the chance — will be your allies in making that change."

Voters in Scotland, who know her well, have warmed to the message that change is possible. Though the SNP only fields candidates in Scotland, Sturgeon is asking voters to support her party so their voices will be heard in London.

But it is also Sturgeon's manner that voters like. She talks about what she watches on television, and is as likely to discuss her shoe selections as she is her desire to get rid of Britain's Trident nuclear submarines, which are based at Scottish ports.

"She's determined, precise. She doesn't make mistakes and she fights elections in a really old-fashioned way — by meeting (voters) in person," Pollack said. "She's on the streets. In a social-media-meets-the-'90s campaign, it's ordinary street politics, but it is being enhanced by a social media."

Polls show the two biggest parties — Labour and the Conservatives — in a virtual dead heat, with neither likely to win a majority. That means Cameron and Labour leader Ed Miliband will have to forge alliances with the smaller parties to form the next government.

While the most natural alliance would be Labour and the SNP, Miliband has ruled out a formal coalition because of the SNP's support for independence and eliminating Trident.

The Conservatives, for their part, are thrilled with Sturgeon's prominence, said Tim Bale, a professor of politics at Queen Mary University of London. In a campaign where his message has failed to energize voters, Cameron now has a clear target: a classic progressive who wants to increase government spending and raise taxes to pay for it.

"He's got the fear factor now," Bale said. "Nicola Sturgeon is the possible answer to his prayers."

Cameron has been making the most of it, taking on Labour and SNP as if they were running together.

"Make no mistake, if Labour and the SNP get into power, you are going to see an alliance between a party that wants to spend, borrow and tax more, with a party that wants to spend, borrow and tax even more," Cameron said on the campaign trail this week. "It might be a match made in heaven for them, but it is a match made in hell for the British economy."

Sturgeon, for her part, keeps holding Labour's feet to the fire, telling anyone who will listen that together, the two parties can remake Britain.

"We have a chance to kick David Cameron out of Downing Street," she told Miliband during a recent debate. "Don't turn your back on it. People will never forgive you."