Force NSPopover to not become first responder with NSTokenField

I'm having a NSTokenField and I'm providing a custom autocompletion inside the popover. Unfortunately as soon as the popover is shown it forces the NSTokenField to resign first responder. Is there a way to show the popover but not to loose the first responder on the NSTokenField?

Overriding NSTokenField's resignFirstResponder causes the NSTokenField to stop working (it doesn't accept any keystrokes). Overriding NSPopover's acceptsFirstResponder method or setting it's behaviour as suggested in this question does not work either.

Edit: The NSTokenField is not inside the NSPopover's contentViewController.view. Edit2: The behaviour like the search bar in the Mailapp would be to optimal solution.

Unfortunately, there’s no clean way to do this. Luckily, though, I’ve done it the ugly way in Delicious Library 3—you need to put this method in a subclass of NSWindow, and make sure the document window in question is that subclass:

- (BOOL)makeFirstResponder:(NSResponder *)responder;
{
    // Prevent popover content view from forcing our current first responder to resign
    if (responder != self.firstResponder && [responder isKindOfClass:[NSView class]]) {
        NSWindow *const newFirstResponderWindow = ((NSView *)responder).window;
        NSWindow *currentFirstResponderWindow;

        NSResponder *const currentFirstResponder = self.firstResponder;
        if ([currentFirstResponder isKindOfClass:[NSWindow class]])
            currentFirstResponderWindow = (id)currentFirstResponder;
        else if ([currentFirstResponder isKindOfClass:[NSView class]])
            currentFirstResponderWindow = ((NSView *)currentFirstResponder).window;

        // Prevent some view in popover from stealing our first responder, but allow the user to explicitly activate it with a click on the popover.
        // Note that the current first responder may be in a child window, if it's a control in the "thick titlebar" area and we're currently full-screen.
        if (newFirstResponderWindow != self && newFirstResponderWindow != currentFirstResponderWindow && self.currentEvent.window != newFirstResponderWindow)
            for (NSView *responderView = (id)responder; responderView; responderView = responderView.superview)
                if ([responderView conformsToProtocol:@protocol(LIPopoverFirstResponderStealingSuppression)] &&
                    ((id <LIPopoverFirstResponderStealingSuppression>)responderView).suppressFirstResponderWhenPopoverShows)
                    return NO;
    }

    return [super makeFirstResponder:responder];
}

Now make sure the popover’s content view subclass implements this protocol:

// NSPopover doesn't respect -acceptsFirstResponder of its content view (Radar 10666891).
@protocol LIPopoverFirstResponderStealingSuppression <NSObject>
@property (readonly, nonatomic) BOOL suppressFirstResponderWhenPopoverShows;
@end

Please also file a bug with Apple to request NSPopover respect -acceptsFirstResponder of its content view; it is 100% the case that when multiple developers file bugs they get fixed.