It was a defining moment: Joe Biden vowed in a searing speech on the first anniversary of the Capitol riot to defend American democracy from mortal danger, while skewering his predecessor Donald Trump. But what comes next?

The veteran Democrat now wants to galvanise his party faithful in the run-up to midterm elections in November, and reboot his stagnant presidency.

But he's taking a major political risk, with little time and limited options to deliver on his promises.

The 79-year-old Mr Biden on Thursday delivered what is widely seen as his best speech to date since taking over the Oval Office, commemorating the attack on the US Capitol by a mob of Trump supporters with a solemn vow to protect the nation.

He shelved his usual easygoing manner and dad jokes for a serious, feisty summary of what happened on 6 January 2021 - and how the nation can move forward amid such a stark political divide.

"I did not seek this fight brought to this Capitol one year ago today, but I will not shrink from it either," he said.

'Come out hard'

For the first time since his inauguration nearly a year ago, Mr Biden took on Mr Trump directly.

Without ever using Trump's name, he savaged the "defeated former president" for questioning his 2020 election win and for sparking his supporters to storm the Capitol.

"Those who stormed this Capitol and those who instigated and incited and those who called on them to do so held a dagger at the throat of America - at American democracy," he said.

"I will allow no one to place a dagger at the throat of democracy."

For David Schultz, a professor of political science at Hamline University in Minnesota, Mr Biden "was in sort of a no-win situation" before the speech.

"Say nothing, and you'd be put on the defensive. Or come out hard like he did" to mobilise his Democrats, which also would spark action on the Republican side, Mr Schultz said.

Indeed, Mr Trump fired back quickly after Mr Biden's speech, as did other Republican heavyweights, accusing Mr Biden of politicising a tragedy to further divide the country.

But there is no mistaking the fact that Mr Biden needs to kickstart his first term in office.

After a more or less harmonious start marked by economic recovery and a waning of the coronavirus pandemic, Mr Biden is certainly bogged down.

The chaotic US withdrawal from Afghanistan has bruised him, and Americans are run down by the ongoing pandemic and the rise of the Omicron coronavirus variant, along with a spike in inflation.

Mr Biden's approval rating is hovering around 43% - a weak level, and a sizeable obstacle to overcome as he tries to push legislation through with a progressive-centrist split in his own party and a razor-thin legislative majority.

For now, the president has had to put his signature social spending bill on the back burner, after Democratic Senator Joe Manchin of West Virginia refused to back it.

'Too little and too late'

And so with the midterm elections - traditionally a tough round for the party in power - on the horizon, Mr Biden has pivoted to focus on the protection of voting rights.

Democrats have accused Republican-controlled state legislatures of enacting laws that would restrict the voting rights of minorities as well as curtail early voting and mail-in casting of ballots.

Mr Biden made a "big promise," Mr Schultz said, and Democrats have an "incredibly narrow window to do something on voting rights" before the midterms, when they risk losing control of Congress.

"If he can't get the voting rights done, that's a major blow for his presidency," Mr Schultz said. A first procedural vote is due later this month.

Some civil rights activists expressed scepticism about the pledges made on Thursday by Mr Biden, who depended on wide support from African American voters in his November 2020 election win over Mr Trump.

"Do you think that he means well? Yes, we believe that he means well. (...) But he really just hasn't done enough over the past year that he's been in office to get voting rights," said Cliff Albright, the co-founder of the Black Voters Matter Fund.

Mr Albright and his organisation have campaigned for voter participation in the southern state of Georgia, where Mr Biden will speak about voting rights on Tuesday.

But for Mr Albright, "it just feels like it's too little and it's too late. And he's just using Georgia as a prop."

"For him to come here now and give this speech without having something major to announce is, you know, at best counterproductive and at worst almost disrespectful."