* Merkel's U-turn on gay rights upsets conservatives
* Risky CDU shifts on conscription, nuclear power, minimum wage
* German leader robs opposition of campaign issues
By Erik Kirschbaum
BERLIN, Feb 26 (Reuters) - Germany's Christian Democrats used to joke that even a drunken supporter woken from a deep slumber could leap to attention and rattle off the party's policy positions.
But Chancellor Angela Merkel has pushed her centre-right party so far from its bedrock conservative roots in the run-up to September's election that even sober CDU voters are having a hard time remembering what their party stands for these days.
The CDU's apparent U-turn this week on rights for gay couples is just the latest example of conservative doctrine being jettisoned in the name of political advantage.
Yet analysts warn the drift left could backfire on Merkel, who is in a tight battle to win a third term in a Sept. 22 election, if she ventures so far to the centre that it alienates core voters on the right.
She has already persuaded her party to sacrifice long-standing conservative tenets such as conscription, nuclear power and university tuition fees.
She now wants the CDU to introduce a minimum wage and over the weekend one of her closest allies signalled the party may also be ready to abandon its opposition giving gay couples the same preferential tax treatment as married heterosexuals.
"The CDU isn't what it used to be," said Gerd Langguth, a political scientist at Bonn University. "It's sacrificing more and more of its conservative core values. That may turn off some of conservative voters but could help Merkel win the election."
The left-leaning weekly Die Zeit noted wryly that the old adage about conservatives knowing party positions by heart because they rarely changed might not fit anymore.
"Before any CDU politician woken at 4 a.m. would know what the party stood for," Die Zeit wrote. But not anymore. "The CDU is angering conservatives by abandoning its old doctrines."
Merkel's Christian Democrats and their Bavarian sister party, the Christian Social Union (CSU), are leading the centre-left opposition Social Democrats (SPD) by a comfortable double-digit margin in most polls. But the CDU/CSU's coalition partners, the Free Democrats (FDP) have slumped below 5 percent in polls and may not even win enough votes to stay in parliament, let alone preserve the centre-right coalition.
That could open the path for the centre-left Social Democrats (SPD) and Greens to form a ruling coalition even if they both end up behind the CDU/CSU on election day. A more likely scenario is a right-left "grand coalition" between Merkel's conservatives and the SPD.
URBAN LOSING STREAK
Many of the positions the CDU has taken are issues that the SPD and Greens have held and analysts say they are designed to rob the centre-left of important campaign issues.
Analysts also note the centre-left now controls the upper house, the Bundesrat, and Merkel is pragmatically switching direction voluntarily before being forced into changing.
"Merkel is taking all the issues away from her opponents so that they won't have any topics to mobilise their own voters with," said Thomas Jaeger, a political scientist at Cologne University. "She knows her own supporters will grudgingly swallow all that, the end of conscription and nuclear power, the introduction of a minimum wage and even rights for gay couples."
Jaeger said Merkel is trying to modernise the CDU after it resisted reforming positions in the past. Its long losing streak in urban centres has underscored the need for action. The CDU is no longer in power in any of Germany's 10 largest cities after losing control of seven in the last three years including Stuttgart, Karlsruhe, Hamburg, Frankfurt, Cologne and Duisburg.
The CDU's shift on taxes for gay couples is particularly striking. The party had rejected a change of position on the issue as recently as December.
"The CDU sees itself above all as a club to keep their chancellor candidate in power, a 'Kanzlerwahlverein'," said Jaeger. "With the push into the centre, the CDU has decided to sacrifice its positions to hold on to the chancellery." (Reporting By Erik Kirschbaum; Editing by Noah Barkin)