I'm having a bit of a problem regarding how to roleplay a schemer character when everyone knows exactly what I am.
I'm the most veteran player in my group, so, for long I have been setting example for other younger players. They know me very well, and know I can be quite of a schemer. In time, this has made them be on their toes with all character I make regardless them being innocent and light or dark and secretive. They don't trust me a bit, and I guess that's okay, it was my actions that set me as this guy who can detach himself from the situation and break all the rules.
Given it's so hard to play a schemer when everyone is so alert, lately I have been playing more goofy characters, or classic action oriented brutes. Still everyone watches closely. Every time it seems I might be planning on stepping out of whats expected of me everyone wants to know what I'm doing, they want an explanation. They know I have a history of suddenly changing and revealing to be something else they didn't expect.
Problem is, my last character in the campaing died (A very good and welcome death) and the DM asked for me to do a certain PC, something that pretty much sticks out as someone who has their own schemes. A politician who has a known connection with an old enemy of the team, but who wants to join forces to defeat a bigger evil. As soon as I make my entrance, everyone is going to go tense and begin schemes of their own, build their webs of secrets and pretty much make my new character feel utterly unwelcome in the team and pushed out of all the decission making. The old apprentices have turned into masters while I was going soft on them and I'm out of my vampire player gears, still they keep seeing me as this all-menacing terror of betrayal.
I know that in the end the problem is metagaming, they're reacting to me not my character. But I don't believe adressing this will solve anything, we will metagame regardless, maybe more subtly, but to the same effect.
I need a blank slate, and my starting position is very disadvantageous. I could always roll another character and play something else, some things are not meant to be, but I trust the DM and if he says he wants for me to do this, I should at least give it a try. So, how can I make the other players trust a character who's very probably not to be trusted?
Well, the campaign is over, and I played this character through. I did keep my usual trend of surprising other players with my schemes, but this time they were all destined to help the group. This created a very unique interaction where some of the characters would see this as my unique way of supporting the mission and play along, while others denounced them as trickery and reveled against them. This lead to a point where the party was morally split in two, had me working harder to try to win over those on the other side who could be persuaded while having a dialectical confrontation with those who would not move an inch. It was fun, but also emotionally exhausting.
In the end my character didn't gain the trust of everyone, but they had the trust of the majority, and for practical purposes that was just what I needed. I've learnt that some players will be more aware of the metagame while others are more inclined to forgive and forget. Overall, it was a very tense experience as the DM wanted to experiment with in-group conflict (not just with me, everyone had a reason to distrust everyone else), but I'm happy to say I wasn't the one giving up and being the traitor, despite our seemingly incompatible goals.
Best Answer
So the DM has asked you to play this type of character, and to have a connection to an enemy of the party. You ask "how can I make the other players trust a character who's very probably not to be trusted?", but has the DM actually asked you to play the character as untrustworthy going forward? That's a whole different kettle of fish from merely having a background that gives the party reason to be suspicious.
If the DM isn't actually working with you on a plot where you eventually betray the party, then it seems to be that you have a very good opportunity to play an interesting in-character story of a dubious character gradually winning the party over. And, in my experience, all you have to do for that to work is not betray them.
The players have all agreed to play a game with you. This game has very strong genre conventions of a group that sticks together through thick and thin. Almost all of the time, the players want to get their characters to that point and will confabulate towards that end. How many times has a new character sought to join an existing group and been quickly accepted, when there's no way an NPC with the exact same behaviour would have become an insider that way?
So long as you seem to be playing your character towards that goal of becoming part of the team and maintaining normal party relationships, they will want to work with you on that. Character-players who have particular reason to distrust your background may want to put on a show of initially refusing to trust you, but they will be far easier to win over (in-character) than really realistic, because the player out-of-character won't want to ruin the game in the real world.
If the players are automatically suspicious that your characters are likely to betray the party then you haven't just been playing schemers, you've been playing jerks (this is not to say that you-the-player have been a jerk; that depends on whether everyone's been having fun, and I assume they have been since they're still playing with you). You can play secretive and scheming characters in a team game just fine. You just need to scheme for the benefit of your friends (or at least not actively against them). Ideally you involve them in your schemes in a positive way (but maybe not the paladin).
So do that, and stick with it for the long term, and in-character trust will come. There aren't any magic words or actions you can take that will automatically fill the trust-o-meter, and there wont' be any singular moment where you can say "ah, that did it" and stop all this onerous not-betraying-them. You just need to have your character sincerely want to work with the party (which might mean putting some thought into designing one whose real goals actually are in alignment with the party's), and then keep doing that.