At the six-month mark of his administration, Donald Trump is less popular than any president elected in the modern polling era. Don’t expect a dramatic reversal of fortune anytime soon.

A POLITICO analysis of Trump’s approval ratings and more than four decades of presidential polling data suggests it’s unlikely Trump’s numbers will significantly change for the better over the next 12 months, imperiling the fate of his stalled legislative agenda and potentially threatening the GOP’s House majority in next year’s midterm elections.

Trump’s approval rating has declined over the course of his young presidency. Gallup data charts Trump’s approval rating gradually dropping over the past six months from the mid-40s after his inauguration to just 39 percent now – the most significant declines have been among moderates, independents and Midwesterners.

How does Trump get above 50? Who can the president woo back to get above water? Our model measures who’s had the most impact on his polling numbers so far and lets you estimate who has to come back into the fold to get him above 50 percent.

Among nearly every demographic category Gallup tracks – men, women, college and non-college educated, whites, minorities and people at every economic level – fewer than 50 percent approve of the president. Only ideological divisions give Trump an edge, where Republicans and conservatives still give him more than 50 percent approval.

“He’s still holding pretty well among Republicans, but he really can’t afford to lose them,” said Jeffrey Jones, senior editor at Gallup. “He’s more likely to go down than up, and if that happens it would be among Republicans.”

According to POLITICO’s analysis, to climb above 50 percent approval by rallying his base alone, Trump would need to have nearly unanimous approval among conservatives. Otherwise he would need to double his support among moderates or quadruple his support among liberals, alone, to get to 50.

That’s largely because of the acute polarization in the country – and polarization that’s focused on Trump specifically. Jones noted that, among those who disapprove of the job Trump is doing as president, most cite his personality and character, and not his policies and positions on issues facing the country. That contrasts with his predecessors, Presidents George W. Bush and Barack Obama: Majorities took issue with their policies and general job performance, but few Americans cited any character issues. That is why Trump remains well behind Obama among most demographic and attitudinal groups after six months in office. Trump’s ratings among liberals are lower than Obama’s among conservatives, and it’s the same for Trump among Democrats versus Obama among Republicans. Trump also badly lags Obama among independents, and Jones noted that that is the source of much of Trump’s decline since his inauguration.

For Trump’s six immediate predecessors, things typically went downhill from here. On average, their approval ratings were 9 points lower at the 18-month mark of their presidencies than after their first six months, according to Gallup Poll data, the most comprehensive source of historical surveys on presidential approval.

That’s a real problem for Trump who, unlike his predecessors, never had broad public support to begin with – and has seen his numbers deteriorate over the past six months. Gallup’s latest weekly average puts him at just 39 percent approval overall. But Trump’s sharp break from past precedent has a silver lining: just as he never had a honeymoon, he may not follow the usual pattern of decline either.

“Generally, if you look at the typical pattern for a president, they start off high in the honeymoon and go down over time,” said Gallup’s Jones. “I’m not sure that that’s going to be the case anymore.”

Production assistance by Sarah Frostenson and Jeremy C.F. Lin.